Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 291043
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
643 AM EDT Sat Apr 29 2017

.SYNOPSIS...
A front will stall near the New York and Pennsylvania border through
tonight and then will gradually push northward into Western New York
on Sunday. This will result in scattered showers and a few
thunderstorms, although most of the weekend will remain dry and
mild. Warmer temperatures will return Monday, with showers and
thunderstorms ahead of a cold front which will cross the region
Monday evening.

&&

.NEAR TERM /THROUGH TONIGHT/...
Radar trends show the bulk of the showers along a stalled frontal
boundary well to our south, with scattered light showers or
sprinkles to the north of this. These will just clip Western
New York this morning.

Today...model consensus stalls the warm front just south of the
NY/PA border. The best chance for additional showers during the
afternoon will be across the Southern Tier. Most mesoscale guidance
develops another convective wave this afternoon, but this will
track along the boundary and mainly pass south of the area.
Expect a mainly dry day with just a small chance of showers
across the Southern Tier. Otherwise, there will be some breaks
of sunshine with highs in the lower to mid 60s in most areas.
The lake breeze will enhance the WNW gradient flow with cooler
temperatures near the lake shores.

Tonight...developing low pressure across the central plains will
begin to influence the stalled frontal boundary an push it northward
into the region as a warm front. Meanwhile, the mid-level thermal
gradient will sharpen across southern Ontario, with an area of rain
expected to develop late tonight. This may bring some showers, and
possibly a thunderstorm to Western New York late tonight, with the
evening hours expected to be largely dry outside of possibly a stray
shower across far western New York. Lows will be in the 40s south of
Lake Ontario with upper 30s east of Lake Ontario. However,
temperatures will rise late in the night across the Western Southern
Tier with the passage of the warm front.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
A closed upper level low will meander across the Southern Plains
today through Sunday, and then towards the western corn belt states
by Monday morning. Ahead of the upper level low deep southerly flow
will transport moisture northward from the Gulf of Mexico.

At surface an area of low pressure forming near SW Texas will slowly
track northward across the Plains, deepening some by a trailing PV
anomaly. This surface low will nudge an elevated warm front
northward, across the Lower Lakes Sunday and to Lake Ontario and
east of Lake Ontario Sunday night. Instability trailing this warm
front will bring chances for showers and thunderstorms through the
day Sunday and into Sunday night. Greatest chances for storms will
come along and north of the warm front. PWATs rising to an inch, and
towards an inch and a third north of the warm front will fuel these
storms. Though instability will be greater south of the warm front,
there will still feature a decent amount of lift north of the warm
front, and it is this lift that will likely form much of the rain
showers and thunderstorms through Sunday night. Greatest rainfall
totals Sunday and Sunday night will likely lie along Lake Ontario
and points eastward. However instability south of the warm front
will still have chances of forming convection, and will continue
with chances PoPs, with any thundertorm bringing locally heavy
downburst of rain.

There will be a great deal of temperature range Sunday, as northeast
and easterly flow across much of the CWA maintain temperatures in
the 50s and lower 60s. However a southerly flow will edge northward
towards the So. Tier Sunday where a few locations will climb into
the mid 70s.

Monday will likely start the day dry, warm and humid as our region
lies within the warm sector of this midwest storm system. A line of
storms will likely form across the western Lake Erie waters midday
Monday, then reaching WNY later in the afternoon. These storms will
have the potential to become strong to severe as a LLJ increases
ahead of the upper level low. 0-6 km Bulk Shear Wind values rise to
65 to 75 knots, and dewpoints rising into the lower 60s supporting
SBCAPE values of a 1000 J/KG or more along with lift ahead of an
approaching cold front should be more than enough to form strong
thunderstorms. There will be a little concern that cloud cover,
especially over the Niagara Frontier may limit some of the
instability and strength of the storms, while farther to the east,
across the Genesee Valley and Finger Lakes region more ample
sunshine will be possible. These storms will continue through the
evening hours, tracking across the CWA. As they reach the Eastern
Lake Ontario region, likely during the evening or late evening
hours, the daytime instability will be waning, and reducing the
strength of the convection.

Temperatures Monday will rise into the upper 70s and lower 80s, with
mid 80s possible within the southern Genesee Valley. Highs Monday
will likely not be as high as this past Thursday, as 850 hPa
temperatures will be a few degrees cooler, and there will likely be
a bit more cloud potential.

Tuesday moist cyclonic flow will continue across our region as the
upper level low, and surface low pass by to our northwest. Gusty
winds will be likely Tuesday, especially northeast of the lakes, and
across the lake Plains where gusts could reach 40 mph. A low level
jet of 45 to 50 knots will reside just above the surface, near 2-3k
feet. However the clouds through the day will limit the daytime
mixing height, with uncertainty still existing as to how strong
these gusts will become. Will continue to mention the strong wind
potential, as well as the strong to severe thunderstorms in the HWO
for now. Temperatures Tuesday will be much cooler, with highs ranging
through the 50s across the region.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Cool and unsettled weather look to be the norm for most days over
the next few weeks as a mean longwave trough remains in place over
the Great Lakes and Northeast, with frequent shortwaves and
associated surface lows bringing periods of showers and fresh
deliveries of cool air.

Tuesday night and Wednesday the deep upper level trough over the
Great Lakes will move east across Quebec and weaken, but will still
maintain enough influence across our region to keep below normal
temperatures in place right through the end of next week. 850mb
temps run from -2C to -4C Wednesday depending on model of choice,
and only improve to around +1C by Friday.

The weather will remain unsettled as well. Tuesday night and
Wednesday the eastward moving trough will combine with cool air
aloft and remaining wrap around moisture to support scattered
showers, especially across the higher terrain with an added boost
from upslope flow. It should briefly dry out Wednesday night as a
bubble of high pressure builds over the eastern Great Lakes and New
England.

By Thursday and Friday of next week another trough is forecast to
dig into the eastern US, and potentially phase and close off into a
mid level closed low. An associated low will form along or inland of
the east coast and move slowly northward. If this materializes, it
will spread clouds and more showers into the region for the end of
the week.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
For the 12Z TAF cycle skies are overcast across the region, but
still mainly in the VFR category. Some light showers or
sprinkles will move across Western New York this morning, but
should generally light with continued VFR conditions. The
exception is across the Southern Tier where there is a bit more
low level moisture and a potential for MVFR or even IFR
conditions this morning. In general, suspect guidance is
overdone but there are patchy IFR cigs along the Lake Erie
shoreline which may move into JHW this morning.

After this, expect mainly VFR conditions with MVFR conditions
at JHW. These trends should continue through this evening, with
only very small chances for showers across Western New York.
These chances will increase late in the night as showers become
more numerous, with cigs expected to lower to MVFR toward
daybreak Sunday.

Outlook...
Sunday...VFR/MVFR with a chance of showers.
Monday...MVFR to locally IFR with showers and thunderstorms
likely.
Tuesday and Wednesday...VFR/MVFR with a chance of showers.

&&

.MARINE...
A frontal boundary will be draped across the lower Great Lakes
this weekend, though winds and waves will remain minimal
through this evening.

Strengthening east to northeasterly winds will bring Small
Craft Advisory conditions to the western Lake Ontario nearshores
for Sunday. Another, stronger storm system may bring another
round of thunderstorms early next week, with high end small
craft conditions likely returning on the lakes by Tuesday.

&&

.TIDES/COASTAL FLOODING...
East to northeast winds will increase late tonight and Sunday,
with waves building across western portions of Lake Ontario.
This combined with already high levels on Lake Ontario has the
potential to result in lakeshore flooding along the shoreline.
There is still uncertainty concerning the placement of the
highest wave heights since even a slight shift to the more
easterly direction would push the highest waves to the Canadian
shoreline. A lakeshore flood watch is in effect for Niagara and
Orleans counties.

&&

.CLIMATE...
The last days of April will finish with above normal temperatures,
warm enough that it will send our climate sites towards a top 5
to 10 warmest April on record. Below are the warmest Aprils on
record.


Buffalo

Rank....Value (F).....Year

1........51.3.........1921
2........51.1.........2010
3........51.0.........1955
4........50.9.........2008
5........50.8.........1878

Current April average temperature through April 28th: 50.4F


Rochester

Rank....Value (F).....Year

1........52.6.........1878
2........52.5.........1921
3........52.4.........2010
4........52.3.........2008
5........51.4.........1915

Current April average temperature through April 28th: 51.5F


Watertown

Rank....Value (F).....Year

1........49.1.........1987
2........48.7.........1955
3........48.7.........2010
4........48.3.........1968
5........48.2.........2008

Current April average temperature through April 28th: 47.6F

Temperature records for Buffalo and Rochester begin 1871, while
Watertown`s history is a bit shorter, with temperature records
beginning in 1949.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lakeshore Flood Watch from Sunday morning through Sunday
     evening for NYZ001-002.
MARINE...Small Craft Advisory from 4 AM Sunday to 2 AM EDT Monday for
         LOZ042-043.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...THOMAS
LONG TERM...HITCHCOCK
AVIATION...APFFEL
MARINE...APFFEL/TMA
TIDES/COASTAL FLOODING...APFFEL/TMA
CLIMATE...THOMAS



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